In U.S. Pat. No. 2,909,522, there is disclosed 2,4-diamino-5-(3,4,5-trimethoxybenzyl) pyrimidine and a process for preparing same. In U.S. Pat. No. 2,888,455, there is disclosed 5-methyl-3-sulfanilamidoisoxazole and a process for preparing same. In U.S. Pat. No. Re. 28,636 there is disclosed a therapeutically active antibacterial composition comprising 5-methyl-3-sulfanilamidoisoxazole, or a salt thereof together with a pharmaceutically acceptable base and 2,4-diamino-5-(3,4,5-trimethoxybenzyl) pyrimidine or a salt thereof with a pharmaceutically acceptable acid.